Initials:
Statistics 100 Spring 2010 Midterm Examination
Solutions Monday, 8 March 2010
Name:
Section TF/day and time:
•
Put your name on the first page and your initials at the top of each page.
•
This is an open book, open notes exam. You may refer to your problems sets and any material
distributed in the course, but all your work must be your own.
•
The exam has 4 problems (each with several parts) and 9 pages. Please check your exam to insure
it is complete.
•
Tables of the Normal distribution will be distributed during the exam. You may also use the tables
in the back of your text.
•
Some questions are more difficult than others, and the questions may not appear in order of
difficulty. Do not spend too much time on any one question; if you find a problem difficult, try
another part of the problem or another problem.
•
Some parts of problems ask more than one question. Be sure to read the questions carefully.
•
Some parts of a question may require the answer to an earlier part. If you cannot solve the earlier
part, you can still receive partial credit for the later parts: make up a reasonable answer for the
earlier part and use that in solving the later parts.
•
You may use (in fact, you are strongly advised to use) a pocket calculator to do the calculations
required on the exam. You may not use your cell phone as a calculator or your laptop.
•
Show your work and explain your reasoning; the final answer is not as important as the process by
which you arrived at that answer. We can more easily give you partial credit if you have explained
your steps.
Problem Scoring
Problem
Point Value
Problem Grade
1
22
2
20
3
31
4
27
Total
100
Page 1 of 9
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Initials:
1. (22 total points)
Summary statistics; the Normal distribution
(a) (4 points) The histogram below shows the distribution of the length at birth (in
centimeters) of 100 low birth weight babies born at the Brigham and Women’s
Hospital in Boston. Is the distribution skewed right, skewed left or symmetric? You
need not justify your answer.
Skewed left.
0
0
.1
.1
.2
.2
.3
.3
Fraction
Fraction
20
20
25
25
30
30
35
35
40
40
length
length
(b) (4 points) The mean length of the 100 babies in part (a) is 36.82 cm. Pick the value
that is the median and justify your answer:
(1) 42 cm
(2) 38 cm
(3) 30 cm
The median is 38cm. The median is larger than the mean in leftskewed data, so 30 is
too small, and the histogram shows that 42 is too large to be the median.
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 Spring '11
 Grandal
 Statistics, Normal Distribution, health care reform, Binge drinking

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